Why won't my wifi stay connected with lion

Question

I recently installed lion on my imac.  Why won't my wifi stay connected after I shut it down

Answer 1

This has been well discussed on another thread here: https://discussions.apple.com/thread/3191630?start=2055&tstart=0
(There appear to be no moderators on these forums to make sure that new threads with the same topic don't get linked to a parent !?)
Anyway... The issues appear for many to be related to a specific Airport card type & firmware version.
I've had constant disconnect problems with my Mini since upgrading to Lion.
My Airport card specs are:
  Card Type:                              AirPort Extreme  (0x168C, 0x86)
  Firmware Version:                    Atheros 5424: 2.1.14.9
Connecting to my Time Capsule distributing on:
          PHY Mode:          802.11a
The Atheros firmware version appears to be the issue depending on certain wifi network conditions.
After some playing about today I think I've managed to force my Mini to connect on a better frequency, without having to roll back the firmware to the Snow Leopard version or mess with the Mini Airport card settings (via Terminal) by changing some settings in my router (Time Capsule).
These are the changes I made:
Airport Utility > Wireless > Wireless Options
Set Radio Mode to 802.11 a/n - b/g instead of 802.11 a/n - b/g/n (Automatic)
Set 2.4 GHz Channel to 13 instead of Automatic
Set 5GHz Channel to 48 instead of Automatic
My Mini now connects on:
PHY Mode:          802.11g
Signal / Noise:          -64 dBm / -96 dBm
Transmit Rate:          54
instead of previously
PHY Mode:          802.11a
Signal / Noise: -73 dBm / -96 dBm
Transmit Rate: 36
This appears now to be stable (no drops in the last 4 hours). It's a low transmit rate still, but better than before.
The iMac is still connecting on
PHY Mode:          802.11n
Signal / Noise:          -69 dBm / -88 dBm
Transmit Rate:          216
and all is right with the world (hopefully for the long term)